Field of the Invention
This invention relates generally to methods for making retreaded tires, and more particularly, to methods for reinforcing or preserving the dimensions or shape of recessed voids in the tire tread during tire retreading operations.
Description of the Related Art
Retreaded tires are commonly manufactured by affixing a new tread atop an existing tire carcass, and securing the tread to the carcass by way of a curing process. In preparation for the curing process, a curing membrane or envelope is arranged about the tread to maintain the tread in a desired position atop the tire carcass and to create a seal between the retreaded tire assembly and the curing membrane. A bonding layer may be interposed between the tread and the tire carcass to promote bonding. Vacuum pressure is applied to the area between the curing membrane and the tread to substantially remove the air between the curing membrane and the tire assembly. The retread tire assembly with curing membrane is placed within a curing chamber, which often referred to as an autoclave, to bond the tread to the tire carcass, where the membrane-covered assembly is exposed to heat and pressure according to a desired curing process.
It is known for retread tire treads to include recessed voids arranged within the tread thickness and recessed from an outer, ground-engaging surface of the tread. For example, recessed voids may comprise circumferential or lateral grooves arranged along the underside of the tread or within the tread thickness between both the outer, ground-engaging surface and the underside of the tread. In prior tire retreading processes, recessed voids can become misshapen or deformed due to curing forces caused by the vacuum pressure and/or curing pressure. Additionally, recessed voids experienced an internal pressure different from the pressure applied to the outer tread surface due to air being trapped within said voids. This pressure differential tends to increase when pressure was applied to the tire by the autoclave. These compression problems tend to reduce void volume and altered the shape of the void, particularly when the tread material around the recessed void was thinner, such as for a thin tread application. This is compounded when bonding material becomes more malleable or fluid as the assembly is heated during the curing process.